The combination supplement was associated with a 17 per cent increase in the anaerobic threshold – the amount of work done before lactic acid begins to accumulate in the blood, according to findings published in the Journal of the International Society of Sports Nutrition.
"The loss of exercise capacity with age often results in a reduction in physical fitness and more rapid senescence,” explained lead researcher Zhaoping Li from the University of California, Los Angeles. “A dietary supplement that increases exercise capacity might help to preserve physical fitness by optimizing performance and improving general health and well being in older people.”
The supplement used in this study was the branded Niteworks supplement (Herbalife International Inc, California), which contains a proprietary blend of L-arginine with L-citrulline, vitamins C and E, folic acid, L-taurine, and alpha lipoic acid.
Sports nutrition is big business, with sales in the US for sports nutrition and weight-loss in 2008 valued at $20.8 billion, according to the Nutrition Business Journal (NBJ). Sports supplements and energy drinks represent approximately 65 percent of that category.
The UCLA researchers recruited 16 men with an average age of 57.6 were randomly assigned to one of two groups. One group received the supplement while the other received placebo for three weeks. A stationary cycle was used to analyse changes in the anaerobic threshold.
At the end of one week of supplementation the researchers noted a 16.7 per cent increase in the anaerobic threshold in the supplementation group, which was maintained until week three, where a 14.2 per cent increase on baseline values was obtained. In the placebo group, however, no significant changes were recorded .
“We've demonstrated a 16.7 per cent increase in anaerobic threshold. This indicates a potential role of arginine and antioxidant supplementation in improving exercise performance in elderly,” said Li.
On the other hand, no changes to the VO2 max were observed.
Commenting on the potential mechanism of action, the researchers focussed on nitric oxide (NO), a molecule involved in many physiological processes, is produced from arginine and inactivated by oxygen free radicals. Supplementation with arginine and antioxidants, the researchers proposed a supporting of the NO system in the cyclists.
“This study indicated a potential role of L-arginine and antioxidant supplementation in improving exercise performance in elderly,” they concluded.
The study was supported by a US National Institutes of Health (NIH) Nutrition and Obesity Training Grant.
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Source: Journal of the International Society of Sports Nutrition
Published online ahead of print, doi:
“Arginine and antioxidant supplement on performance in elderly male cyclists: a randomized controlled trial”
Authors: S. Chen, W. Kim, S.M. Henning, C.L. Carpenter, Z. Li